Topic 3 - Particle Model of Matter

• Density = how compact mass in for an object
• Find density of a regular objects = find volume with measurements (with ruler, vernier callipers or a micrometer) and measure mass on a balance
• Find irregular object density = use a displacement can and whatever volume of water is displaced is the same volume as the objects and measure mass on a balance
• Irregular shape density practical:

  1. Measure the mass of the objects first on a balance
  2. Fill displacement can until it is just below the spout
  3. Place a measuring cylinder under the spout
  4. Gently lower the object into the can
  5. Take reading in the measuring cylinder - eye level and from the bottom of the meniscus
  6. Use the density equation to calculate the density
• Solids:

  • particles in regular arrangement (lattice)
  • Vibrate in fixed positions
  • Cannot be compressed
• Liquid:

  • particles have no regular arrangment
  • able to move past each other
  • cannot be compressed
• Gas:

  • Particles are far apart
  • Move randomly and at fast speed (high energy)
  • Can be compressed
• Solid to liquid = melting

  Liquid to gas = boiling/evaportation

  Gas to liquid = condensing

  Liquid to solid = freezing/solidifying

  Solid to gas = sublimation
• The melt/boil, energy must be supplied to overcome the electrostatic forces of attraction between particles
• Internal energy = sum of kinetic energy and potential energy of all particles in a substance - only one can change at a time
• Heating Curve graph

  
• The temperature doesn't increase when a substance is changing shape due to the energy being used to break the bonds between the particles
• Specific heat capacity = the energy required to raise the temperature of 1kg of a substance by 1 degree
• Specific Latent heat = how much energy is required to change the state of 1kg of a substance
• The particle theory of gas:

  Gas pressure is a result of the particles colliding with the walls of its container, exerting a force outwards
• By heating a gas, you increase the particles' kinetic energy, meaning they collide more frequently and with a greater force - there is an increase in pressure (if the volume stays constant)
• To compress a gas, you must exert a force on it - this is called doing 'work' on a gas
• If a gas is compressed at a constant temperature:

  pV = constant

  p and V are inversely proportional so if one doubles, the other halves
• Density Practical:

  1. Regular = measure sides and mass with a ruler and a balance to calculate density
  2. Irregular =
  3. Measure the mass of the (dry) object
  4. Fill a displacement can with water until it is just under the spout
  5. Place a measuring cylinder under the spout
  6. Gently place object in
  7. Measure the water in the measuring cylinder and that is the volume of the object
  8. Calculate density with the equation